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<h1>Memory</h1>

This driver implements read and write access layers of features contained
entirely in memory.  This is primarily useful as a high performance, and highly
malleable working data store.  All update options, geometry types, and 
field types are supported.<p>

There is no way to open an existing Memory datastore.  It must be created
with CreateDataSource() and populated and used from that handle.  When the
datastore is closed all contents are freed and destroyed. <p>

The driver does not implement spatial or attribute indexing, so spatial and
attribute queries are still evaluated against all features.  Fetching features
by feature id should be very fast (just an array lookup and feature copy). 
<p>

<h2>Creation Issues</h2>

Any name may be used for a created datasource.  There are no datasource
or layer creation options supported.  Layer names need to be unique, but
are not otherwise constrained.<p>

Feature ids passed to CreateFeature() are preserved <i>unless</i> they exceed 
10000000 in which case they will be reset to avoid a requirement for an 
excessively large and sparse feature array.<p>

New fields can be added to layer that already has features. <p>


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